One current method consists of acquiring an image or a film of the surface. Said image or film is next viewed by an operator, who indicates the defects that he has identified.
However, the operator may not identify a defect due to lack of attention. Furthermore, the criteria making it possible to judge a defect are subjective, i.e., the definition of what constitutes a defect may vary depending on the operator.
One solution often implemented to offset these problems is to have the film or image viewed by several operators. Furthermore, surface image examples are used in order to show what is or is not a defect.
However, the examples shown are neither exhaustive nor reproducible.
In the event of a defect, experts are consulted. Many discussions between experts then take place, the experts not necessarily agreeing with one another.